1. Field of the Invention
The present invention relates to an information recording apparatus, such as a write-once-type optical disc recorder, for recoding information onto an information recording medium, such as a write-once-type optical disc, and an optimum recording laser power detecting method which is executed on such an information recording apparatus.
2. Description of the Related Art
For example, on an information recording/reproducing apparatus for recording information onto an information recording medium, such as an optical disc, the optimum recording power of a laser beam is set by Optimum Power Control (OPC) processing according to the type of the optical disc, the type and the recording speed of the information recording/reproducing apparatus, and the like. Namely, the calibration of the recording laser power (i.e., the calibration of the recording power of the laser beam) is performed. This corresponds to variations in characteristics of an information recording surface of the optical disc. For example, if the optical disc is inserted or loaded and a command of writing is inputted, light intensity is changed sequentially step-by-step and the data for trial writing is recorded into a Power Calibration Area (PCA), by which so-called trial writing is performed. After that, the data for trial writing recorded in this manner is reproduced. The reproduction result is judged by a predetermined evaluation standard, and the optimum recording laser power is set.
More specifically, for example, in the case of a DVD-R (DVD-Recordable), the PCA (i.e., the OPC area, or the recording area for OPC) is provided with about 400 clusters, for example. One cluster is equivalent to 16 sectors, for example. Here, the “cluster” is a data management unit on a disc-shaped memory device and the smallest unit upon error-correcting. On the other hand, the “sector” is the smallest data management unit by pre-format address information in which the record data is error-correctable. One sector is equivalent to 26 sync frames, and one sync frame (hereinafter referred to as SF as occasion demands) is formed from a pre-pit which is the smallest unit of an address structure. The one SF is regarded as a unit of a power-step in one OPC processing, for example. Using the unit of the power-step, if the one OPC processing is provided with 26 power-steps, for example, the shortest pit length, 3T, and the longest pit length, 11T, of an 8/16 modulated test signal are recorded with respect to 26 SF with 26-stage laser powers, and the OPC processing is performed. Here, “T” is a standard clock cycle. For example, in the case of the DVD-R, 0.133 (μm)/3.49 (m/s)=about 38.2 (ns). Namely, the 26 SF (i.e. one sector) are used in the one OPC processing. With respect to each SF, an “OPC pattern”, which is a predetermined pattern including a plurality of recording pits for trial writing (i.e. OPC pits), is recorded for each power-step. At this time, by setting the number of the power-steps used for the one OPC processing to be equal to or less than the number of the sync frames included in one sector, it is possible to perform the one OPC processing with the one sector. Therefore, for example, in one disc or one PCA provided for the one disc, it is possible to perform about 6400 times of OPC processing corresponding to the cluster total number (about 400 clusters). Incidentally, in this case, one cluster is equivalent to 16 sectors, but how many sectors the one cluster is equivalent to is various depending on the type of the medium. The above technique is disclosed in Japanese Patent NO. 3159454, and Japanese Patent Application Laying Open NO. 2002-352517.
However, according to the above-described technique, if the recording medium is a so-called write-once-type recording medium, for example, a write-once-type optical disc, such as the DVD-R, rewriting is not performed in the PCA because it uses the data management unit of the pre-format address (sector) information, which is an accessible unit, and because the unit corresponding to the sector is large in a large-capacity medium. This causes such a problem that the number of the OPC processing is limited by the size of the data management unit of the pre-format address information in the PCA. Particularly, with respect to a larger-capacity write-once-type recording medium, the chance or the number of writing-once or additional recording for one medium increases, so that the number of the OPC processing increases. As a result, if the OPC processing is executed as conventionally performed, the PCA is possibly used up before recording is performed onto an entire recording area, which is a technical problem.